1. Field of the Invention
The present invention relates generally to a retainer for chip-type electronic parts for temporarily holding chip-type electronic parts, and more particularly, to a retainer for electronic parts used, for example while measuring properties of chip-type electronic parts, placing markings on the surfaces of chip-type electronic parts, or containing many electronic parts in a housing in order to package the electronic parts in a tape-type packaging structure.
2. Description of Background Art
FIG. 1 is a partially-broken perspective view showing the foregoing type of retainer for chip-type electronic parts as conventionally used, and FIG. 2 is a cross sectional view showing main parts of the retainer shown in FIG. 1.
A conventional retainer 1 for electronic parts is constructed by using a rectangular plate 2 made of metal with a predetermined thickness. Many retaining holes 4 are formed in alignment, each holding a respective chip-type electronic part 3 such as a multilayer capacitor.
The plane shape of each of the retaining holes 4 is a shape corresponding to the plane shape of the electronic part 3. Each of the retaining holes 4 comprises a first opening 4a having a depth corresponding to the thickness of the electronic part 3 and a second opening 4b connected to the first opening 4a and having a diameter smaller than that of the first opening 4a. A stepped portion 4c on which both ends of the electronic part 3 are deposited interconnects the openings 4a and 4b.
The electronic part 3 is inserted in the first opening 4a in the retaining hole 4 in the direction represented by an arrow in FIG. 2.
When electrical properties of the electronic part 3 are measured and the electronic part 3 is subjected to marking, the electronic part 3 must be fixed in the retaining hole 4. Accordingly, when the conventional retainer 1 for electronic parts having the above-described structure is used, the electronic part 3 is held in the first opening 4a by applying suction by vacuum from below through the second opening 4b.
With the above-described holding method, however, when a clearance exists between an inner surface of the first opening 4a and a side surface of the electronic part 3, it is difficult to precisely position the electronic part 3 in the first opening 4a. Consequently, there is a problem that it is difficult to make measurements of, and to place markings on the parts with high precision.
The prior art retainer for electronic parts shown in the perspective view of FIG. 3 has been considered as being a solution to the above-described problem. In FIG. 3, portions corresponding to those in the structure shown in FIGS. 1 and 2 have the same reference numerals and hence, the description thereof is not repeated.
The retainer 5 for electronic parts shown in FIG. 3 is constructed by using a rectangular plate 6 made of metal. A plurality of elastic body-attaching holes 7 are formed in the plate 6. Elastic bodies 8 made of, for example, rubber are integrally adhered in the elastic body-attaching holes 7, respectively, by molding. Retaining holes 9 each having a diameter slightly smaller than that of the external form of an electronic part are respectively formed in the elastic bodies 8.
In the retainer 5 for electronic parts shown in FIG. 3, electronic parts are respectively held in the retaining holes 9. Consequently, the electronic parts can be subjected to processing such as marking.
In the retainer 5 for electronic parts, no clearance occurs between an inner surface of the retaining hole 9 and an external side surface of the electronic part so that the electronic part is held due to the elasticity of the elastic body 8. Accordingly, the electronic parts can be easily positioned.
In the retainer 5 for electronic parts shown in FIG. 3, the elastic holding power received from the inner surface of the retaining hole 9 depends on the size of the retaining hole 9 relative to the external form of the electronic part, that is, the wall thickness of the elastic body 8. For example, the elastic holding power is decreased when the wall thickness of the elastic body 8 is decreased so that the diameter of the retaining hole 9 becomes large, while being increased when the wall thickness of the elastic body 8 is large so that the diameter of the retaining hole 9 becomes small.
Accordingly, when the wall thickness of the elastic body 8 adhered to an inner surface of each of the elastic body attaching holes 7 in the plate 6 is formed with low precision, the electronic parts are likely to receive non-uniform elastic holding power from the inner surfaces of the retaining holes 9. More specifically, some electronic parts are held by relatively weak elastic holding power. As a result, difficulties are liable to arise in exactly positioning each of the electronic parts in the retaining hole 9 to measure its electronic properties, for subjecting each of the electronic parts to required processing such as marking or taping, and, further, for variously handling the parts when, for example, storing or shipping the retainer 5.
In order to eliminate the above described difficulties, it is necessary to increase the precision of the wall thickness of the elastic body 8. If this is done, however, the cost of manufacturing the elastic body 8 is high.